This invention relates to an explosion and flame proof electrical connector protective assembly. More particularly, this invention relates to a new and improved explosion and flame proof electrical connector protective assembly which is especially suitable for use in extremely hazardous environments such as, for example, Class 1, Division 1 and 2 hazardous areas associated with oil rigs and the like.
Off-shore oil rigs and the like present many difficult problems in terms of worker safety, fire and explosion prevention, etc. In fact, it is well known that such rigs can be quite hazardous due to the flammable gasses and liquids which are commonly associated with the oil drilling art. Specifically, certain areas in and around an oil rig platform are deemed more hazardous or dangerous in terms of fire and explosion possibilities than other areas. Thus, locations on a rig are typically divided into several hazardous categories.
In the United States, the classification of such hazardous areas are set forth by the National Electric Code (NEC). The areas of greatest danger are termed Class 1, Division 1 and Class 1, Division 2 areas or locations. Class 1 locations are those in which flammable gasses or vapors are or may be present in the air in quantities sufficient to produce explosive or ignitable mixtures. Other countries have promulgated similar classifications. For example, in Europe, the classifications are set by the International Electrotechnical Committee (IEC) defining a Zone 1 area as roughly equivalent to Class 1, Division 1 area with Zone 2 being similar to Class 1, Division 2. The IEC also has a Zone 0 which can be included in Class 1, Division 1 under NEC classifications. It should be understood that for the sake of simplicity and for the purposes of this patent application, a discussion of "classified hazardous areas" or "Class 1, Division 1 areas" will encompass all of the well known names for such hazardous areas.
Electrical components and other equipment located in an area classified as hazardous (i.e., Class 1, Division 1 or Zone 1) must be designed to meet rigorous and comprehensive International or U.S. safety regulations and standards before they can be used therein. In fact, a component must undergo a thorough certification procedure by an applicable testing facility by Underwriter's Laboratory (U.L.) or British Approvals Service for Electrical Equipment and Flammable Atmosphere (BASEEFA) for example, to assure that the components do meet the requirements of organizations such as the NEC or IEC. This certification procedure is principally aimed at assuring flame and explosion proof protection. It follows then, that an uncertified component, such as an uncertified electrical connector, cannot be used in Class 1, Division 1 or similar hazardous areas.
As mentioned above, in a Class 1, Division 1 area on oil rigs and the like, only certified electrical connectors and other components may be used therein due to the hazards posed by disconnections and the risks of resultant sparks and explosions. However, it is well known to those skilled in the art that practical and commercially economical "certified" connectors for instrumentation are not presently available. Those commercial explosion proof connectors which are availabe are excessively large, expensive and limited to power circuits with a limited number of wires. Typically, electrical connections between a pair of cables or a cable and electric or electronic components are effected in one of two ways. A first method (which is also most commonly utilized) is to directly wire (i.e., hardwire) cables and components and so avoid any separate connector structure. However, hardwiring suffers from several drawbacks including expensive, labor intensive assembly; and difficult, time consuming and expensive location and repair of damaged equipment. It will be appreciated that if even one component or circuit malfunctions, then the entire assembly must be disassembled and re-wired. Thus, hardwiring can typically or at least potentially be quite unreliable and undesirable especially in portable or reconfigurable situations.
A second method of effecting an electrical connection in a Class 1, Division 1 hazardous area of an oil rig or the like is to enclose standard uncertifiable connectors within a conventional explosion proof box. However, the use of such a standard, well-known explosion proof box is undesirable for a variety of reasons. For example, such conventional boxes are quite large, bulky and unwieldy and hence, become a mechanical design constraint. This is especially true as Class 1, Division 1 areas on oil rigs often necessitate electrical connections in tight areas of limited space. Also, conventional explosion-proof boxes are usually constructed of cast iron and necessitate a large heavy cover which is bolted on the box. Obviously, the heavy cast iron construction is undesirable as is the use of a separate cover since the cover is often complicated and may require the presence of a seal and/or accurately machined surfaces.